The c1c2/c2c2 genotype which affects the transcriptional activity of CYP2E1 was associated with a significant reduction of the RBC index (MCV and MCH) in SCA-HU+ patients, suggesting that the variant allele c2 compromises the beneficial effect of HU to increase the RBC index, as seen in the present study and shown by Pallis et al. [34]. The gene discussed is CYP2E1; the disease is autosomal dominant cerebellar ataxia.